Home » Public Forums » GMCnet » Re: [GMCnet] Finally about to pull the 403
| Re: [GMCnet] Finally about to pull the 403 [message #208864] |
Sun, 26 May 2013 14:59  |
KB
Messages: 1262
Registered: September 2009
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> If it's quiet at idle and starts to clatter at engine speed (not 1/2 speed) pace starting at about 1500 RPM it's probably a connecting rod bearing at the crank end. The extra slop can allow the piston to rap the ledge on the head once piston speed is high enough. Sounds worse than it is but will have to be fixed before ruining the crank. Now if you can detemine which one it is by plug wire pulling and sound pattern changing--- wondering if its worth lifting engine enough to pull the pan and rebearing that rod. However what caused it is the question and that could be an oiling issue needed full deep cleaning. Out of coach unfortunately.
The current theory is it's a rod bearing. I pulled all the spark plugs
and they looked fine. While moving, I listened with a hose and metal rod at the
alternator, water pump, tranny, and valve covers and couldn't locate it.
It does have exhaust leaks, which we suspected but couldn't prove
was the culprit. For most of the drive, it seemed to be related to throttle
position rather than RPM -- ie, when coasting down hill or at low throttle,
it'd stop. Since we have EFI with EBL, we have logs of it happening --
the knock sensor picked it up and backed off the timing.
Coming up our steep hill for the last 5 miles of the trip, it seemed
quiet under load, but knocked in between load and coasting. Once home
though, there was a steady knock at idle, and we can get it to
rap once or twice if we rev it. Could, in theory, be something to do
with belts/pulleys, but the metal flakes kinda discount that idea.
I considered pulling the pan and trying to see what's up, but
since that's also quite labor intensive, I haven't a clue what
I'm looking at, and don't know what caused it or how extensive
the damage, the easiest course seems to be an engine swap.
We also considered getting a cheap USB bore camera and looking
through the oil drain hole to see if anything obvious was visible.
Not sure how useful that would be though.
Guess we'll see what the oil analysis says and go from there,
but I'm not feeling optimistic. At least it got us home.
thanks
Karen
1973 23'
1975 26'
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Karen
1975 26'
San Jose, CA
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| Re: [GMCnet] Finally about to pull the 403 [message #208869 is a reply to message #208864] |
Sun, 26 May 2013 15:18  |
mickeysss
Messages: 1476
Registered: January 2012
Karma: 0
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Senior Member |
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Some times a push rod is bent
M 77 PB. Ca.
Sent from my iPhone
On May 26, 2013, at 12:59 PM, KB <kab7@sonic.net> wrote:
>> If it's quiet at idle and starts to clatter at engine speed (not 1/2 speed) pace starting at about 1500 RPM it's probably a connecting rod bearing at the crank end. The extra slop can allow the piston to rap the ledge on the head once piston speed is high enough. Sounds worse than it is but will have to be fixed before ruining the crank. Now if you can detemine which one it is by plug wire pulling and sound pattern changing--- wondering if its worth lifting engine enough to pull the pan and rebearing that rod. However what caused it is the question and that could be an oiling issue needed full deep cleaning. Out of coach unfortunately.
>
>
> The current theory is it's a rod bearing. I pulled all the spark plugs
> and they looked fine. While moving, I listened with a hose and metal rod at the
> alternator, water pump, tranny, and valve covers and couldn't locate it.
> It does have exhaust leaks, which we suspected but couldn't prove
> was the culprit. For most of the drive, it seemed to be related to throttle
> position rather than RPM -- ie, when coasting down hill or at low throttle,
> it'd stop. Since we have EFI with EBL, we have logs of it happening --
> the knock sensor picked it up and backed off the timing.
>
> Coming up our steep hill for the last 5 miles of the trip, it seemed
> quiet under load, but knocked in between load and coasting. Once home
> though, there was a steady knock at idle, and we can get it to
> rap once or twice if we rev it. Could, in theory, be something to do
> with belts/pulleys, but the metal flakes kinda discount that idea.
>
> I considered pulling the pan and trying to see what's up, but
> since that's also quite labor intensive, I haven't a clue what
> I'm looking at, and don't know what caused it or how extensive
> the damage, the easiest course seems to be an engine swap.
> We also considered getting a cheap USB bore camera and looking
> through the oil drain hole to see if anything obvious was visible.
> Not sure how useful that would be though.
>
> Guess we'll see what the oil analysis says and go from there,
> but I'm not feeling optimistic. At least it got us home.
>
>
> thanks
> Karen
> 1973 23'
> 1975 26'
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Finally about to pull the 403 [message #208901 is a reply to message #208864] |
Sun, 26 May 2013 22:22 |
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On 5/26/2013 12:59 PM, KB wrote:
> The current theory is it's a rod bearing. I pulled all the spark plugs
> and they looked fine.
Karen,
I had similar symptoms to yours and was convinced it was a
rod. Turned out to be 1 missing and 1 loose bolts on the torque converter.
tt
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Terry Taylor
'74 ex-Eleganza SE
San Lorenzo, CA
http://www.n6mon.org
http://dldesignstore.com
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| Re: [GMCnet] Finally about to pull the 403 [message #208916 is a reply to message #208864] |
Mon, 27 May 2013 04:24 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I tend to over think everything when I have engine problems. I did it again today. I had loud random heavy metallic banging on my 2 cylinder 22 horse garden tractor. It would not bang at very slow idle speeds sitting still, but any higher engine speed it got real noisy even when the tractor was not moving.
I'm thinking something is bouncing around inside a cylinder or maybe a starter gear hanging slightly. After taking several things apart and removing the deck belt, the banging was still there just as bad as ever. Finally removing the drive belt caused it to go away. Now I thought it had to be in the zero turn dual drive system.
I removed several more parts including the drive belt idler and found everything looked OK. Then I noticed a slight fresh mark on the idler arm. It had been hitting a motor mounting bolt. The 57.5 inch 10 year old belt had stretched slightly allowing the arm to hit the motor mount bolt. I bought a 57" belt at TSC and installed tonight. That took care of the problem.
My point is I was convinced that I had a major engine problem when it was only a stretched 10 year old belt. It only took 1.5 hours to find it. So check out all of the other possibilities, no matter how remote, before pulling that engine.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Finally about to pull the 403 [message #208921 is a reply to message #208864] |
Mon, 27 May 2013 07:12 |
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WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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Senior Member |
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The current theory is it's a rod bearing.
thanks
Karen
1973 23'
1975 26'
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[/quote]
I can tell you that it is a sickening feeling. We had just a dab over 6k when the number 7 rod bearing went to hammering. Pulled off immediatly and got the flat bed called. Saved everything but that rod. Your oil analysis will tell the tale.
Wishing you the best.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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